Field of the Invention
The present invention relates to a communication apparatus, and particularly relates to a communication apparatus, for example, configured to perform communication with another apparatus at the matched baud rate, these two apparatuses each including a microprocessor or the like capable of changing the baud rate to a desired rate; and a lens apparatus and an image pickup apparatus including the communication apparatus.
Description of the Related Art
Heretofore, there has been a method for allowing two apparatuses to set a baud rate using baud rate setting data when performing data communication. In this method, one of the two apparatuses does not change the baud rate, while the other apparatus sequentially changes the baud rate, thereby setting the baud rate allowing normal transmission and reception.
For example, Japanese Patent Application Laid-Open No. 2004-64616 (hereinafter, JP-A 2004-64616) discloses a method for allowing two apparatuses to match their baud rates by using baud rate setting data when performing data communication, in which the transmission side apparatus transmits the setting data at a baud rate unknown to the reception side apparatus, while the reception side apparatus sequentially changes and matches the baud rate with the baud rate of the transmission side apparatus.
Japanese Patent Application Laid-Open No. H05-236048 (hereinafter, JP-A 5-236048) discloses a configuration for matching baud rates using baud rate checking data, in which a transmission side apparatus transmits the checking data while sequentially changing a baud rate, until a reception side apparatus replies that the baud rate is matched, thereby matching the baud rates.
In the conventional techniques disclosed in JP-A 2004-64616 and JP-A 5-236048, if both of the two apparatuses to perform data communication change their baud rates, the baud rate allowing normal transmission and reception cannot be set. For example, in both the methods described in JP-A 2004-64616 and JP-A 5-236048, one of the apparatuses changes the baud rate in order to match the baud rate with the fixed baud rate of the other apparatus. Nonetheless, suppose a case where the other apparatus also changes the baud rate by the same process. In this case, when the one apparatus changes the baud rate, the other apparatus also simultaneously changes the baud rate to a different baud rate. Consequently, these changes in baud rate never come to an agreement, making it impossible to set a baud rate allowing normal transmission and reception in some cases.